1. Field of the Invention
This invention relates to a method for regeneration of an aged coke-selectivated crystalline aluminosilicate zeolite catalyst by treatment with hydrogen under particular conditions.
2. Description of the Prior Art
It has heretofore been known to employ coke-selectivated catalysts comprising a crystalline aluminosilicate zeolite having a silica to alumina mole ratio of at least about 12 and a constraint index between about 1 and about 12 for conversion of various organic compounds involving reactions such as alkylation, disproportionation, isomerization, cracking, polymerization, aromatization, etc. These catalysts have been found to be particularly useful in selective processes, such as selective toluene disproportionation and aromatics alkylation with olefins. The coke-selectivated catalysts so employed slowly deactivate with time on stream ultimately making regeneration thereof necessary.
Regeneration has heretofore been carried out by contacting the aged catalyst at an elevated temperature with an oxygen-containing atmosphere, e.g., air, to effect removal of coke therefrom. Such procedure has served to restore the initial activity of the catalyst but has resulted in very substantial reduction in selectivity of the catalyst, approaching that of the unselectivated zeolite. Thus, after air regeneration, the catalyst has required reselectivation, i.e., controlled precoking, to restore the desired initial selectivity.